This invention relates to a zoom lens system. More particularly, it relates to a zoom lens system that is suitable for use with a small video camera, e.g., with an image size of 1/2 inch, that can be manufactured at a relatively low cost, that is compact and which yet is bright and capable of zooming at a ratio of up to about 6.
With the recent expanded use of small video cameras, a need has arisen to use as an imaging lens a zoom lens that is bright, that is capable of high zooming ratio, that is compact and which yet can be manufactured at low cost. Among the zoom lens systems that have been developed with a view to meeting this need are those which are described in Unexamined Published Japanese Patent Application Nos. 213816/1986 and 24214/1987.
In these conventional zoom lens systems, aspheric surfaces are used to reduce the number of lens elements, whereby the need for compactness and low cost is partly met. However, aspheric surfaces are generally more difficult to produce than spherical surfaces. Further, the resulting lens systems are not completely satisfactory in terms of compactness.